High throughput printing systems, such as those used in high speed printers and color copiers, or large format devices put heavy demand on an ink delivery system. The printhead must operate at a very high frequency. At the same time, print quality expectations keep rising. In order to maintain high print quality, the printhead must be able to rapidly eject ink without causing large fluctuations in the printhead pressure level.
One approach to this is to provide a pressure regulator integral to the printhead. The regulator receives ink at a first pressure and delivers ink to the printhead at a controlled second pressure. In order for this control to work, the first pressure must always be greater than the second pressure. Because of dynamic pressure drops, very high pixel rate printing requires that the first pressure be at a positive gauge pressure.
One example of an ink cartridge that can be pressurized is described in U.S. Pat. No. 4,568,954. Other references include U.S. Pat. Nos. 4,558,326; 4,604,633; 4,714,937; 4,977,413; Saito U.S. Pat. Nos. 4,422,084; and 4,342,041.
A simple way to provide pressure is to surround a collapsible bag with a pressurizable shell. In theory, such a shell can be simple in construction. However, the ink container exterior should perform a number of functions. It must provide keying, aligning and latching functions to provide the mechanical interface to the product. It should protect certain ink container features that are easily broken or contaminated. It should provide user-friendly grasping surfaces. When these requirements are integrated with the pressure chamber requirements, the outside of the ink container becomes very difficult to design and manufacture. What is needed is a way of offering the functionality just described while providing for efficient molding and assembly.